The U.S. Coast Guard and Long Beach Fire Department today are investigating the source of a possible oil spill in Long Beach near Alamitos Beach.

Witnesses reported seeing tar balls on the shoreline at approximately 4:30 p.m. near the 400 block of East Shoreline Drive and fire department officials joined the Coast Guard in responding to the scene, U.S. Coast Guard Petty Officer Aidan Cooney told City News Service.

“When our team arrived there was no oil or any tar balls along the shoreline and any oil that was in the water had dissipated,” Cooney said.

Cooney said the source of the slick was unknown.

“We’ll continue to monitor the situation in Long Beach,” he said.

CBS 2 reported no marine or wildlife were harmed by the slick.

A team from the state Fish and Wildlife Department will also participate in monitoring any new potential spills.