Crews are nearly done cleaning up thousands of dead fish that washed ashore in Keansburg earlier this week.

Crews from the state Department of Environmental Protection were out Wednesday using large vacuums to suck up all of the fish from the waterways. Officials say the raking of the beach stopped around mid-afternoon due to high tide coming in, but the majority of the fish were picked up.

The state Department of Environmental Conservation says the recent heat wave caused the water temperature to rise, creating a lack of oxygen in the Waackaack Creek. The fish then suffocated and started piling up on the shore.

"This is primarily a natural phenomenon, but it is exacerbated by polluted runoff, including fertilizers from lawns, which is why preserving stream corridors and buffers is important," said NY/NJ Baykeeper Deputy Director Greg Remaud in a statement.

Dead fish were also found in Natco Lake, Thornes Creek and along the Raritan Bayshore, according to officials.

Officials are expected to monitor the area over the next few days to make sure more fish do not wash up.