A mainlander has been arrested in Shenzhen for sending a letter bomb after trying to blackmail his Hong Kong businessman boss. The bomb, carried in a speed delivery envelope and left at the businessman's door, was picked up on July 27 by a neighbour who thought he would be out of town for a while. The envelope was put in the neighbour's shoe cabinet and exploded at night. No one was injured. Detectives found a letter at the scene threatening to bomb the businessman's home if he did not pay 70,000 yuan (HK$65,550). The businessman had received other threatening letters. Public security officers arrested the suspect this month after learning that he was the only one of the victim's employees in Shenzhen to have visited his home.