Pay Beach in Oak Bluffs has reopened for swimming, one day after it was ordered closed due to elevated levels of bacteria.

Oak Bluffs health agent Shirley Fauteux said Wednesday that a routine water sample taken on July 9 revealed higher than allowed levels of enterococcus, organisms that may indicate the presence of bacteria found in sewage. The beach was reopened Thursday when a subsequent water sample showed bacteria levels well below the range of what is considered safe for swimming.

All other Island beaches tested negative for enterococcus bacteria and remained open during that time.

However, a popular children’s swimming pond in West Tisbury has remained closed due to bacteria since July 3.

Mr. Powers said he is testing the water at Seth’s Pond daily, and will re-open the pond when water samples come back clean.

This is the fourth time the pond has been closed since June due to bacteria, he said. In some of those instances the pond was closed for only one day following a rainfall event, which can affect bacteria levels, Mr. Powers said.

Last year elevated readings prompted a number of beaches and ponds to close intermittently throughout the summer, with no apparent cause for the bacteria found. Some officials speculated that faulty testing or sample anomalies could have been to blame.

A complete list of all water samples taken on Martha’s Vineyard beaches, as well as an up-to-date list of beach closures can be found on the Bureau of Environmental Health’s website.