A team of United States environmental protection regulators has accidentally released 3.8 million litres of waste water into a local river system.

A large portion of the river was dyed orange by the spill, which contained sediment and metals that had been held behind a barrier near the abandoned Gold King Mine.

The Environmental Protection Agency (EPA) said the accidental release let water into Cement Creek, which flows into the Animas River in San Juan County.

A number of workers were in the EPA crew, using heavy equipment to pump and treat the waste water when the breach occurred., but none were injured.

Health officials have issued warnings to water users downstream to turn off their intakes and avoid recreational activity in the water until the contamination has passed.

The nearby city of Durango says tap water is safe, as it has stopped pumping water from the Animas River and is instead drawing water from the unaffected Florida River.

The EPA will perform sampling at downstream locations to confirm when the release has passed.

It is expected to assess damage near the mine and look for any residual releases of mine water.