A 50-year-old homeless, convicted felon admitted Thursday in U.S. District Court that he stole mail from post office boxes at the downtown post office on Merchant Street.

Richard Cui pleaded guilty to one count of mail theft. He faces a maximum five-year prison term at sentencing in April. He also will have to pay restitution, but Assistant U.S. Attorney Amalia Fenton told Senior U.S. District Judge Susan Oki Mollway that the government is still calculating the amount.

In the meantime Cui remains in custody without the opportunity for release.

In exchange for his guilty plea, the government has agreed to drop eight other mail theft charges against him and promised not to charge him with additional crimes based on information it discovered after his federal grand jury indictment in August and arrest in September.

Fenton told Mollway that between May and August Cui stole mail from post office boxes at the Merchant Street post office on multiple occasions. He gave the stolen mail to others in exchange for drugs and money.

She said Cui didn’t know how to alter checks he found in the stolen mail, so he gave those and stolen credit cards to others who knew how to fraudulently use them.

Cui told Mollway that he exchanged the stolen mail “to get drugs” and sometimes for money, but “mostly drugs.” He also said he tried to use debit cards he found in the stolen mail.

The U.S. Postal Inspection Service said it started an investigation when numerous post office box customers at the post office filed complaints of missing mail.

U.S. Postal Inspector Brian W. Shaughnessy said surveillance cameras recorded Cui using a screwdriver to break into post office boxes. He said upgrades are being made to the boxes and that other security enhancements have been put in place.