The state Department of Health is posting warning signs and collecting water samples around Palolo Stream after an estimated 1,000 gallons of wastewater overflowed on a vacant lot at 3472 Kaau Street near 9th Avenue.

The Clean Water Branch said last night that a grease blockage caused the spill of about 2,000 gallons, half of which entered the stream through a storm drain.

The spill was reported at 6:45 p.m. after wastewater overflowed out of a manhole when a six-inch terra cotta pipe clogged, the city Department of Environmental Services said. City crews cleaned, disinfected and deodorized the area.

The public is advised to stay out of the stream.