OAKLAND — Operations at one of the Port of Oakland’s largest terminals were suspended for several hours Thursday when longshoremen walked off the job in response to nooses found on the property in recent weeks.

They returned to work Thursday afternoon after negotiations and normal operations resumed, officials said.

The longshoremen at the Oakland International Container Terminal left about 9 a.m., an hour after they had started for the day, under the order of union officials, officials said.

By late morning, about 100 union longshoremen at the terminal, 1717 Middle Harbor Road, were on standby waiting to hear if they would return to work. Container trucks were backed up all around the port and on Interstate 880.

Officials with the International Longshore and Warehouse Union were working to obtain surveillance tape that could reveal who is responsible for the nooses. Arbitration on whether the union members will get paid for their time during the walkout was under way.

An unspecified number of nooses have been discovered at the terminal in recent weeks, including one found Thursday morning, union officials said. The nooses have been left on a fence, the ground, and on trucks.

Derrick Muhammad, the union’s secretary-treasurer, said a noose had also been found about 10 days ago. In November, someone spray painted a racial slur against African Americans on a piece of port equipment, he said.

“We believe it’s a bonafide health and safety issue because of the history behind the noose and what it means for black people in America,” Muhammad said. “This is a dangerous occupation already. This adds something that totally makes people feel uneasy, makes people feel unsafe and it’s distracting. We need our people to be as focused as possible.”

Robert McEllrath, International President, International Longshore and Warehouse Union, said in an e-mailed statement that “the ILWU is a progressive and diverse union, and we reject in the strongest possible terms racism in all its forms. This matter is being vigorously investigated.

“The display of a hangmen’s noose for the second time in two weeks at the work site is inexcusable and expressly prohibited conduct under the terms of the ILWU-PMA collective bargaining agreement. The Union is committed to securing a non-discriminatory work environment for all individuals working at the ports.”

The terminal, SSA Marine, had no statement Thursday morning.

Mike Zampa, Communications Director for the Port of Oakland spokesman confirmed operations had resumed.

He said the port was told a “symbol associated with racial bigotry was discovered on the terminal property. The Port of Oakland does not tolerate bigotry or discrimination of any kind. That is explicit in our policies and in our day-to-day operations.

Zanka said the port has “been in close contact with the terminal operator. They are investigating the incident and taking steps to prevent a reoccurrence. They’ll apprise us of those next steps.”

Staff writer David DeBolt contributed to this report.