Sen. Frank Lautenberg Hospitalized

Updated 11:29 a.m. ET

A bleeding ulcer is behind the hospitalization of longtime New Jersey Sen. Frank Lautenberg, an aide said Tuesday.

Chief of staff Dan Katz said that no discharge date is set, but that he expects the 86-year-old Democrat to be released soon.

The senator was taken to a hospital Monday after becoming lightheaded and falling at his Cliffside Park home. He later underwent a successful endoscopy procedure, spokesman Caley Gray said.

Lautenberg is expected "to make a full recovery and will be back to work soon," Gray said.

His office announced Monday night that he was in great spirits, was joking with doctors and would stay there overnight for routine observation. The name of the hospital where the senator is being treated was not released.

Lautenberg returned Friday from a trip to Haiti with a congressional delegation. He was scheduled to discuss the trip and the U.S. aid effort for the Caribbean nation, which is recovering from a devastating earthquake, at a news conference Tuesday. His office has not said whether he is still expected to attend.

Lautenberg, born in Paterson, first came to prominence as chairman of Automatic Data Processing, a payroll services company he founded with two friends in 1952.

The liberal Lautenberg has been a staunch gun control advocate and critic of the tobacco industry. He wrote laws to ban smoking on domestic airline flights and to institute a national minimum drinking age of 21.

He has been back in the spotlight recently as a critic of the Transportation Security Administration after a January security breach at Newark Liberty International Airport. He also was active in the effort to end a custody dispute with Brazil involving the son of Tinton Falls, N.J., resident David Goldman.