LONG BEACH (AP) — Two days after black crude oil was found in a major water pipeline, crews were still working to locate the source of the contamination that forced water to be shut off to hotels and parts of the Port of Long Beach.

Oil mixed with the water was discovered during a routing test of fire hydrants at the port on Wednesday.

READ MORE: How To Watch The 2021 Primetime Emmy Awards

Crews believe they’ve isolated the pipeline where the contamination originated, but hotels and restaurants were still being advised to avoid using their water for consumption, port spokesman Art Wong told the Long Beach Press-Telegram Thursday.

He said tests were continuing and he expected officials would receive clearance to turn the water back on Friday.

The water has been shut off since Wednesday at the Maya Hotel and Residence Inn as well as part of the port.

Officials were investigating the cause.

“It’s a real mystery,” Wong said. “It’s very strange that crude oil and water are mixing.”

READ MORE: Man Struck Multiple Times In Daylight Shooting In Riverside

Workers and guests at the Queen Mary complex and all the port’s shipping terminals have been advised not to come into direct contact with water.

No other part of Long Beach has been affected, Wong said.

No sicknesses have been reported and no oil leaked into harbor waters or storm drains, the Press-Telegram reported.

Critical water, such as for fire hydrants, remains available.

The contamination was discovered in the water main as port workers opened and flushed fire hydrants to make sure they were working.

MORE NEWS: Emmys Vow A Good Time After Bleak Year; 'Crown' May Rule

The port, meanwhile, remains open for business, though workers are having to drink bottled water and use port-o-potties.

(© Copyright 2010 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)