OTTAWA - Officials at New Brunswick's Point Lepreau nuclear power station say it will take some time to determine why radioactive heavy water leaked from a piece of equipment this week.

Staff were evacuated from the nuclear plant near Saint John after four to six litres of the heavy water spilled Tuesday from a piece of monitoring equipment.

Station director Wade Parker told the Canadian Nuclear Safety Commission in Ottawa on Thursday that the equipment had been thoroughly checked.

"We took great pains to make sure this equipment was ready for service, including leak checks, pressurized with gas, and everything was acceptable," he said during a conference call to the commission's public hearing. "We will get the details on this and determine what caused this to happen."

The heavy-water system was being refilled at the time of the spill as part of the utility's plan to restart the generating station after a refurbishment that is three years behind schedule and $1 billion over the original $1.4-billion budget.

The refurbishment of the aging Candu-6 reactor is intended to extend the life of the reactor by another 25 to 30 years. NB Power expects to have the power plant up and running by next fall.

The refilling process for the heavy water is on hold until the cause of the leak is determined. The spilled water has been cleaned up and there were no injuries.

The commission commended NB Power for its handling of the incident.

"Cleanup took place as per procedure," said Greg Rzentkowski, director general for power reactor regulation. "The potential risk to the environment was negligible and there were no workers or public health implications."

Burt Valpy, a commission staff member, was at Point Lepreau when the spill occurred. He said the utility did a good job preparing staff on safety procedures in the event of such an accident.

"Our only concern at this point is in terms of NB Power determining what led to the release of the spill and modifying their moderator refill procedure as required," he said.

Rzentkowski said a final report is expected by the end of the month.