About 2,500 gallons of wastewater flowed from manholes on Na Wai Eha Street in Wailuku Wednesday, according to the county Department of Environmental Management.

The overflow, caused by grease in a mainline, was discovered at 5 p.m. and was stopped within two hours.

Wastewater flowed from sewer, along the roadway, and into a storm drain, eventually reaching a retention basin that does not connect to the ocean, the department said.

The mainline was flushed, the Department of Health was notified, and warning signs were posted along the retention basin.