A Baptist University student was in critical condition last night, and another listed as stable, as police investigated whether the truck that allegedly rammed into a taxi that hit them as they crossed a Kowloon Tong street on Thursday was being operated illegally. Police arrested the truck driver, 63, on suspicion of dangerous driving causing grievous bodily harm after the 9.15pm crash at the junction of Waterloo Road and Hereford Road. After investigating further, they also arrested his co-worker, 44, who a police source said was following him in a tow truck. Police are investigating whether the truck driven by the older man should have been towed, rather than operated on city streets. "They are co-workers and responsible for transporting the truck," the source said. Both men were released on bail and are required to report back to police later this month. Neither has been charged. One of the victims, a 20-year-old woman studying social science, was in critical condition in Queen Elizabeth Hospital last night. The other, a 19-year-old man studying communications, was in stable condition. The two, who were crossing with a green pedestrian light, did not know each other, police said. The truck driver told police his brakes failed when he tried to stop for the taxi, senior police inspector Harry Ho Kwan-ho said. The truck has been confiscated for inspection. They said the taxi stopped at a red light before the truck hit it from behind. The collision caused the taxi to plunge forward and knock down the two students, who were then trapped by the truck. The woman was said to have been pinned by one of the truck's rear wheels. The man's family told local media after visiting him in hospital that he had suffered scratches to his limbs. The taxi driver, 57, and his female passenger, 54, were slightly injured. They were discharged after treatment. A video taken by a third vehicle's camera and circulated online showed the taxi stopped at a red light at the junction, and the truck ramming into it from behind, sending both vehicles into the crossing. A pedestrian who could be seen walking across the road in the video appeared to get back to his feet and run out of the way after the truck moved out of the crossing. Baptist University said it was saddened by the crash and would offer necessary assistance to the students' families. It said teachers and their classmates had visited the injured students in the hospital.