BALTIMORE (WJZ) — What’s in the water? People–shocked to see parts of the Inner Harbor turned a milky white and green–as hundreds of dead fish float to the surface.

Meghan McCorkell has more as environmental experts look for a cause.

Preliminary tests show little to no oxygen in the water. Now experts are trying to find out why.

Right in the shadow of the National Aquarium, a troubling sight on the Inner Harbor.

“It was white, chalky. It looked almost like weird pool water,” said Greg Linares.

From Sky Eye Chopper 13, you can see the murky green water spilling out from the Jones Falls into the Inner Harbor.

“This lighter green colored water that you can see contrasted against the Harbor has moved about another 100 yards into the Harbor,” said Captain Jeff Long.

At least 200 dead fish have floated to the surface.

“We collected water samples today. We’ll be doing more tests on those tomorrow,” said Jay Apperson, Maryland Department of the Environment.

The MDE hazmat team is investigating the cause, and says the recent heat wave could be a factor.

“It’s probably a sequence of events that has to do with too many nutrients being in the water. That creates a series of reactions and events that leads to no oxygen in the water,” said Apperson.

They’re also working with the city to check for any leaks or overflows in any sewage lines in the area.

Environmental experts say the water in the Inner Harbor could stay murky for up to two weeks.

People walking along the Harbor were surprised to see all the dead fish.

“I saw it and said, ‘Oh, what is going on here?'” a woman said.

“It’s very surprising. I never heard of something like that,” a man said.

Now the experts will try to figure out how it happened.

Hundreds of fish were also found dead in the Inner Harbor last summer. Experts said that was due to an algae bloom.

Local advocates are pushing to have the Harbor clean enough to swim in by 2020.