BOSTON -- The operator of a heavily trafficked drawbridge linking Boston and Chelsea was taken into protective custody on Saturday after he failed to raise the bridge for an approaching ship and police allegedly found him intoxicated at his post, Chelsea police said.

Officers were dispatched to the Andrew P. McArdle Bridge at about 4 p.m. on Saturday when a tugboat trying to pass underneath the structure notified police that it was unable to make contact with the drawbridge operator, according to Chelsea Police Chief Brian Kyes.

The tugboat driver told police that he radioed ahead to have the bridge raised, but received no response from the operator. The driver said he then blew his horn and rang a bell when he arrived at the bridge, but still received no response.

Kyes said officers traveled to the bridge for a well-being check and found Robert E. Finn, 49, “in a state of intoxication,” at his monitoring station. Finn, who is an employee of the Boston Department of Public Works, was taken into protective custody and replaced by another bridge operator, Kyes said.

Kyes did not specify what condition the drawbridge operator was found in, but protective custody is invoked when police deem an individual to pose an immediate threat to themselves or to the public.

The Coast Guard confirmed that an operator at the McArdle Bridge, which is also known as the Meridian Street Bridge, was replaced by another worker at about 5 p.m. on Saturday.

Dot Joyce, a spokeswoman for Mayor Thomas Menino, said Sunday that Finn has been placed on paid administrative leave pending the outcome of an investigation. He has not been charged by Chelsea police.

The area of the Chelsea River that the bridge straddles is a passageway to fueling stations further inland from Boston Harbor.

Edward Medico, a worker at the nearby Fitzgerald Shipyard, told NewsCenter 5’s Cheryl Fiandaca that tankers frequently pass under the bridge to reach the fueling stations. Medico, who said he witnessed the incident on Saturday, estimated that about 20 ships pass underneath the bridge each day.

Vehicles also use the bridge to travel between East Boston and Chelsea on Meridian Street.