Recent testing of the lakes, located within Rock Creek Regional Park, showed elevated levels of microcystin, a toxin that can cause liver damage in both humans and pets if ingested.

WASHINGTON — Visitors to Lake Needwood and Lake Frank in Montgomery County are being advised to exercise caution due to high levels of a toxin caused by algae.

Recent testing of the lakes, located within Rock Creek Regional Park, showed elevated levels of microcystin, a toxin made by blue-green algae. The substance can cause liver damage in both humans and pets if ingested.

Montgomery Parks advises visitors to take the following precautions:

Avoid direct contact with water while boating or fishing.

Do not swim in the lakes, as it is prohibited.

Keep dogs on a leash, and don’t let them have any contact with the water.

Wash hands thoroughly before eating, drinking or smoking if you have made contact with the water.

Only eat properly cooked muscle meat of fish caught in the lake.

Boating and fishing are still allowed. Portions of both lakes, however, may be contaminated for the rest of the season, park officials said.

For more information, visit the Montgomery Parks website.