Updated Saturday 9:41pm from the Associated Press:

The Coast Guard says a section of the Ohio River in Louisville was re-opened Friday after a tugboat and coal barge accident forced its closing.

Coast Guard officials say a towing vessel was pushing 15 loaded coal barges when it hit the 2nd Street Bridge on Tuesday.

The crash caused the 15 barges to break free. The Coast Guard says six barges have sunk.

Coast Guard officials announced late Friday that the Ohio River was reopened to all vessel traffic from Twelve Mile Island to McAlpine Lock and Dam.

The Coast Guard said Saturday that traffic is only permitted during daylight hours and with an assist vessel.

A city official says the coal spill is not expected to affect drinking water.

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At least 6,000 tons of coal sank into the Ohio River, and federal authorities are continuing to work on a plan to save the remaining barges pinned against the McAlpine Dam.

Fifteen coal barges broke free from a tug boat headed north up the Ohio River earlier this week. Six barges were recovered while another nine floated downriver.

By Friday afternoon, four barges had sunk into the river, each carrying at least 1,500 tons of coal, said U.S. Coast Guard spokesman Lt. Cmdr. Michael Metz.

The Army Corps of Engineers is working with the Coast Guard on a plan to safely recover the remaining barges, but they’ll have to overcome a few challenges.

Water levels along the Ohio were higher than normal on Friday and are expected to fluctuate over the weekend. At the same time, at least two more barges are at risk of sinking, said Shawn Kenney with the Army Corps of Engineers.

“There are a couple additional ones that are comprised,” Kenney said. “So we can’t say with certainty that no more will sink.”

The state’s Energy and Environment Cabinet is monitoring the situation and doesn’t believe the coal poses an environmental threat.

“Right now we don’t see any reason that there might be an environmental emergency, but we are monitoring the situation,” Mura said.

While coal does contain dangerous heavy metals like arsenic and mercury, coal in its rock form is less harmful than after it’s been burned. Nonetheless, cities that pull their water from the river were notified about the accident by the Ohio River Valley Water Sanitation Commission.

The tug boat is owned by the Tennessee Valley Towing company and was headed for Trimble County, Metz said. The company did not immediately return a request for comment.

So far it is unclear how much the cleanup will cost or who will pay for it, but Metz said it’s common for the responsible party to pick up the tab.