HONG KONG (AP) — Cleanup efforts are underway in Hong Kong after white blobs of congealed palm oil washed up on the city’s shores following a collision between two ships.

Authorities have closed more than a dozen beaches, including two on Tuesday, since the spill was reported over the weekend, though the government says the substance isn’t dangerous.

Marine officials say the ships collided in the Pearl River Delta estuary southwest of Hong Kong on Thursday, but Hong Kong authorities were not notified by their counterparts in mainland China until two days later.

The congealed palm oil resembles clumps of snow or pieces of Styrofoam and has a consistency similar to Play-Doh. It has been spotted blanketing Hong Kong beaches and floating in the water.

Cleanup crews had collected more than 50 metric tons of the stuff by Monday, and filled 110 garbage bags with it on just one beach on Lamma Island, the government said. It has deployed helicopters and nine ships to help find and collect the waste while workers at public beaches are using absorbent blankets and strips to contain the mess.

Palm oil is commonly used in food packaging and cosmetics. Environment Undersecretary Tse Chin-wan told reporters that it is nontoxic and that there has been no sign of widespread impact on marine life. Tse said that no more than 1,000 metric tons leaked from the stricken ship.

Environmentalists worry about the harm the substance could pose to Hong Kong’s already polluted waters, and to fish and other animals that eat large amounts of it.

Hong Kong is made up of a peninsula attached to mainland China’s southern coast as well as about 260 islands, many of them small and uninhabited.