City of Waco and Texas Parks and Wildlife Department (TPWD) officials trying to safeguard Lake Waco against the zebra mussel menace have scored a tentative victory, according to the Waco Tribune-Herald.

A report to TPWD last week showed no traces of zebra mussel larvae or DNA in samples taken from the lake Dec. 4.

A colony of zebra mussels was discovered at Lake Waco in September. Officials installed a football field-sized tarp to smother the zebra mussels before lake temperatures dropped to the ideal breeding range. The tarp will be removed in about a month.

TPWD biologist John Tibbs said, “If the tarp strategy proves to be successful, it could be useful for containing other zebra mussel populations, but only in limited circumstances. It is rare to find a small population like the one at Lake Waco. More commonly, zebra mussels spread throughout a lake before they are detected.”