Four suspects have been detained for putting down three cars as collateral in order to borrow money and then stealing the cars back without paying off the loans, police said on Thursday.

Police in Songjiang District started to investigate the case after the loan firm boss reported in late November that he lost contact with some clients who used three cars as collateral in September, but the cars went missing before the money was returned.

The three received 540,000 yuan (US$78,000) in loans, police said.

Four people suspected to be involved in the fraud were caught earlier this month.

One of the suspects, a man surnamed Sun, allegedly confessed that he changed the locked tire on his car with a backup tire from the trunk and drove away from an underground parking lot where the car was kept.

Surveillance cameras in the parking lot catch the suspects driving their cars away on different dates.