HOUSTON -

Federal investigators raided a Houston hospital Wednesday.

About a dozen federal agents showed up at Riverside Hospital, 3204 Ennis, with search warrants. They brought along a truck to cart away boxes of documents.

Around the same time, agents arrested Mohammad Khan, the hospital's assistant administrator, at his home.

Khan has been accused of conspiring to defraud taxpayers out of $116 million.

The indictment alleges that Khan and unnamed co-conspirators billed Medicare of psychiatric services that were not needed or were never provided.

Investigators claim Khan paid kickbacks to assisted living centers and group homes to send patients to Riverside Hospital.

Hospital officials said Riverside, a Houston institution for 94 years, has not done anything wrong.

"I have no concerns at all," spokeswoman Tasha Armstead said. "I feel very comfortable knowing Riverside is doing all the right things, and there shouldn't be any issues at all. Our attorneys are handling the rest of it."

Khan appeared in court Wednesday and asked for a court-appointed attorney. The judge denied that request, telling Khan that he can afford to hire his own attorney.

Prosecutors claim Khan is a flight risk and have asked that he be held without bond.