"We found the money stored under the bed at their homes and they admitted they took the money on Gloucester [Road] after getting off the taxi they were in," said police chief inspector Addy Li Chi-kin at a media briefing outside an industrial building on 20 Sheung Yuet Road in Kowloon Bay where the male suspect arrested.

"During the mission police have found HK$165,000 in cash at the male suspect's home in Kowloon Bay. In-depth investigation is still under way in the female suspect's home Tseung Kwan O."

The two suspects were located after officers reviewed CCTV footage and the licence plates of vehicles present at the time of the incident.

"We will arrest as soon as possible all the people who have been identified," Li said.

Witnesses told reporters that they saw mainland tourists leaving their coaches and taking stashes of the spilled cash with them.

Asked what the police could do if those who had snatched the spilled banknotes had already left the city, Li said: "It depends whether police have already known and verified the identities of the suspects.

"We hope those who had picked up cash on the day can return the cash to the closest police station as soon as possible so that police can handle [the matter] promptly."

On Thursday afternoon, police said that 27 people had handed over cash, including two individuals who returned HK$1 million and one person who handed in HK$2 million.

The police had previously asked the public to help return the money that went missing in the frantic scramble, most of it in HK$500 notes, the equivalent of about US$65.

The vehicle was transporting a total of HK$270 million in cash. The HK$500 and HK$1,000 banknotes were contained in 30 plastic boxes.

Three of the boxes with a total of HK$52.5 million cash were dropped from a door of a G4S van. A total of HK$15.23 million in cash was later found to be missing.

Bank of China (BOCHK), which hired G4S to deliver the banknotes, said in a statement on Thursday that the security service company had offered an apology and promised to pay for the losses.

“G4S has apologised for the incident and will hold liable to all the losses incurred based upon the contract engaged with BOCHK,” the statement reads.

The bank said it had “constantly requested” the contractor to “put in place and effectively implement a set of stringent operational and control procedures.”

“Immediately following the incident, BOCHK has already urged G4S to investigate into the incident by identifying root causes and adopting prompt remediation to prevent further recurrence in the future.”

Watch: People scramble for cash after van spills banknotes on busy Hong Kong street

Despite the excesses of cash spilled, the van operated by three guards continued driving to G4S’s headquarters in Cheung Sha Wan, Kowloon, 14 kilometres way, until the incident was reported.

A picture taken by an SCMP photographer at the scene showed a single bundle of HK$500 notes wrapped in plastic, with a sticker on the side, bearing the figure HK$500,000, from the Bank of China (Hong Kong).

One witness, an office worker at a nearby building who requested anonymity, told the Post he saw a "regular looking Hong Kong lady" pick up at least 10 cash bricks before quickly walking off, although he could not verify the denominations of notes she was carrying.

"I saw a lady with 10 of them, easily. She looked like a very regular Hong Kong lady. She had an armful of bricks of cash - it was a much as she could carry. She just disappeared into the depths of Wan Chai," the witness said.

The eyewitness said he had just left his office building when he noticed traffic grind to a halt.

"It all started slowing down and I noticed a couple of blue boxes on the road. I thought a lorry had lost some of its load. I saw a few people in the street picking up what I thought were iPhone boxes. As I got closer I saw they were wrapped bundles of bills.

"As well as the packed money there were HK$500 bills lying on the road itself.

"At first people did nothing, then one person went into the road," the witness said, before telling how others quickly followed suit.

"You couldn’t make it up. There were 20 or 30 people picking up cash from the road on Christmas Eve. They looked like schoolkids who knew they were being naughty, but thought, ’this is a once in a lifetime thing’. Everyone had the same look on their face."

Pictures posted on social media showed a taxi driver abandoning his car in the middle of the busy dual carriageway and scrambling around on the tarmac in an effort to collect some of the cash.

Armed police quickly arrived on the scene and cordoned off two lanes of Gloucester Road. The eyewitness said officers became angry as those collecting notes initially ignored their call to get out of the road, before the site was cordoned off.

Three boxes, which appeared to be containers used by security firms to transport large amounts of money, could be seen stacked up in the middle of the road being guarded by dozens of police, including armed officers. Representatives of the security firm G4S were also at the scene.

Sheeta Leung Hui-kwan, a spokeswoman for G4S Hong Kong, said: “We are still having an internal investigation and we found that something went wrong with the door on the left side.

“Our guards [conducted] the job according to the standard procedure but during the incident there were three guards in the van.

“Our guards reported the incident when they reached Cheung Sha Wan, our head office. Due to the code of conduct and comfort problems, we will not put any guards inside where we store the money.

“The normal procedure is, if the bank wants to release the money somewhere, we will collect the cash and then put it in our vault, and we have to count the cash for security, and then we will deliver it according to the bank’s order.”

G4S said the banks normally only record the serial numbers for new notes. The security firm was only responsible for counting the cash and making sure the amount was correct, she added.

Regarding potential responsibility for the losses, Leung said “it is for sure” G4S was liable to cover the lost funds.