Even after Westport spent millions to rid its middle school of PCBs, the cancer causing substance continues to show up in testing.

The school committee is scheduled to hear more this Wednesday at 5 p.m. (after Shorelines went to press) about the latest round of testing. Those September tests revealed the presence of PCBs at more than twice the federal safe standard level in one of the school's guidance offices. School officials say that the office is not being used by students or staff.

The tests showed PCB levels in that office of 630 nanograms, more than twice the U.S. Environmental Protection Agency's 300-nanogram standard.

This week's discussion comes on the heels of the signing last Monday, Jan. 14, by the Westport Board of Selectmen of a voter-approved loan for $4.3 million to pay for PCB removal and unrelated green repair work at the middle school.

The 19-year loan has an annual average interest rate of 2.78 percent with interest expected to total over $1 million.

PCBS (polychlorinated biphenyls) are a known carcinogen.

In the middle school, the substance was found during the summer of 2011 in window caulk that subsequently leached into surrounding masonry over  the years and eventually into the air inside the school. PCBs were also round in the glue used to secure roof panels at the school.

That caulking work apparently dates back to the 1970s before the use of PCBs was banned in 1979.

The town spent around $3.4 million removing and replacing all known caulk and sealants containing PCBs and also replaced masonry near contaminated windows. The source of this latest high reading has not yet been announced.