Dozens of shipping containers tumbled at the Port of Long Beach on Tuesday morning when a cargo vessel listed to one side, U.S. Coast Guard officials said.

       The incident occurred around 8:44 a.m. when containers aboard the vessel Mississippi began collapsing at the Pier G container terminal, according to Coast Guard Sector Los Angeles-Long Beach watchstanders. They reported that 20 containers fell into the water, while another 50 containers collapsed on the ship.

       No injuries or pollution were reported, but cargo operations were temporarily suspended as emergency crews responded to the scene, Port of Long Beach spokesperson Art Marroquin said.

       The U.S. Coast Guard established a safety zone around Pier G-232 while multiple agencies, including the Long Beach Fire Department, Police Department and Port Police, rushed to the terminal. A Coast Guard helicopter from Air Station Ventura conducted initial aerial surveillance of the area, Coast Guard officials confirmed.

       Aerial footage captured by ABC News' Los Angeles station, KABC, showed the Mississippi tilting to one side after two stacks of containers collapsed.

       "A unified command has been established," Coast Guard officials said in a statement. "The cause of the incident is under investigation."

       ABC News' Jenna Harrison contributed to this report.

       This is a developing story. Please check back for updates.