An Australian state closed two beaches after dead fish and an unusual off-white foam washed ashore while surfers reported feeling unwell, officials said on Tuesday.

A microalgal bloom created by unusual weather conditions was suspected to have sickened humans and marine life as well as creating the foam that has covered hundreds of meters (yards) of coastline, South Australian Environment Protection Authority principal scientific officer Sam Gaylard said.

“It is very concerning,” Gaylard told Australian Broadcasting Corp.

“It is unusual at this scale. At this time of year, when the weather conditions allow, we do occasionally get isolated blooms, but something of this scale is definitely a little bit unusual,” Gaylard added.

Waitpinga Beach and neighboring Parsons Beach, both south of the South Australia state capital Adelaide, have been closed to the public since Monday in response to a “fish mortality event in the area,” the Department for Environment and Water said in a statement.

“The beaches will be re-opened as soon as possible,” the department said.

Dozens of dead fish have reportedly been washed shore.