State health officials removed warning signs posted at a contaminated drainage ditch near the bike path at Hekaha Street in Aiea after water samples showed acidity levels had returned to normal on Monday.

The Health Department posted the warning sings Friday after a chemical spill killed more than 600 fish. 

The department’s Clean Water Branch on May 12 received the report of a fish kill and milky-white discolored water with a strong “cleaning agent” like scent on May 12.

A nearby business, MOC Hawaii, reported that on May 11, the company accidentally spilled about 70 gallons of an industrial cleaner into a storm drain inlet that drains to the Aiea ditch. The Health Department said the company is cooperating with the investigation into the incident.

Initial test results indicated lower than normal PH levels in the water, suggesting contamination from an acidic compound which could include cleaning solvents or solutions, the Health Department said.