Visitors to John Martin Reservoir State Park are advised to avoid any contact with the reservoir and the Arkansas River beginning Monday as water contaminated by a 4.2 million-gallon untreated sewage spill in Pueblo moves downstream, Colorado Parks and Wildlife officials said Sunday.

The spill began Wednesday and was stopped on Thursday, with high levels of E. coli found in water samples taken downstream of the contamination point. The affected water is expected to reach the reservoir Monday morning.

Working alongside the Colorado Department of Public Health and Environment, CPW is keeping park staff informed as the spill moves closer.

“I’m grateful for the communication that has kept us up to speed from the onset,” said park manager Dan Kirmer. “While we cannot fix what is coming downstream, we have an opportunity to prepare and communicate with our visitors before it arrives.”

While the park will remain open, visitors should avoid any activity that involves contact with the reservoir or the Arkansas River, including (but not limited to) swimming, wading, tubing, paddleboarding and fishing. Pets should also be kept away from the water, officials said.

The spill comes as park staff are dealing with other, unrelated water quality issues involving cyanobacteria, also known as blue-green algae. The reservoir was recently downgraded to caution level “yellow,” while Lake Hasty, another body of water at the park, is closed to full-body water contact after a recent test showed dangerously high levels of the algae.

“Lake Hasty will not be impacted by the sewage spill, but its existing algae restrictions remain in place,” Kirmer said. “We will continue testing and communicating with our visitors as conditions change.”

Warning signs will be posted around the park and the reservoir, officials said.