The Maine Department of Environmental Protection reported Monday that some progress has been made in cleaning up an oil spill in a small pond in Calvary Cemetery, first noticed Aug. 7 by cemetery workers.

The state, which is not sure how much oil was spilled, is leading an investigation in an effort to place responsibility and recover the cost of cleanup. Andrew Flint, an environmental specialist with the state, said the focus is on the Rigby train yard in South Portland, which has had problems with oil drainage in the past.

“We did have some issues of concern there. They had past issues with oil drainage,” Flint said Monday.

It is believed that a 10,000-gallon oil/water separator that collects oil runoff from the Rigby train yard failed, and drained oil along with the water after heavy rain Aug. 6.

Jon Woodard, of the state’s Bureau of Remediation and Waste Management, said the only detail the state is sure of is that the oil entered the pond through the storm drain system for the Cash Corner area.

The amount of oil spilled into the approximately two-acre pond was originally estimated to be 100 gallons. Woodard said that was a conservative estimate, though he is not sure exactly how much oil drained into the pond.

“It’s really hard to quantify once you start collecting it,” Woodard said Friday.

Clean Harbors Environmental Services, based in Norwell, Mass., was hired to suction oil and contain the spill. Crews worked last week and into this week, laying down boom fences and raking and collecting contaminated vegetation from the shoreline. Woodard said workers are now focusing on the bushes between route 1 and the shore, which are still oiled. All the oil has been removed from the water. Woodard expects the clean up to last through the end of this week.

“Each day there will be less and less,” said Woodard.

The Maine Department of Inland Fisheries and Wildlife is working alongside Clean Harbors to rescue animals affected by the oil. As of Monday, 10 painted turtles had been caught in traps, according to biologist Judy Walker. A wood duck was also found, heavily oiled, and did not survive. Walker said she was more optimistic about the turtles’ prognoses, because they are hardy animals.

“I’m hopeful that all the turtles will make it,” said Walker.

All animals are being transferred to the Center for Wildlife in Cape Neddick. Walker said she would ideally like to release the animals back into the cemetery pond, but that would depend on the result of the cleanup. She said she would look for animals until she is sure that all affected animals have been removed from the pond, which she said could easily take another week, or more.

Meanwhile, Flint said, if the train yard is the culprit, the state would impose fines and other measures.

“Certainly there would be additional corrective actions beyond (fines),” said Flint.

The Rigby yard is owned by Pan Am Railways, based in Billerica, Mass. At press time, Pan Am had not responded to repeated phone calls seeking comment for this story.