Work will begin as soon as Monday to rebuild the brick tower that collapsed in dramatic fashion Wednesday atop Lawrence’s oldest church.

“We’ve already got scaffolding scheduled to come back in,” said Tom Brown, a member of Plymouth Congregational Church, 925 Vt., who helps oversee the building’s maintenance.

Brown didn’t have an estimate Thursday on how much it would cost to rebuild the tower, which fell apart Wednesday afternoon as a crew filled its hollow center with mortar. The idea was to stabilize the tower and prevent it from falling during heavy winds, as two other towers at the church did in a spring 2006 microburst storm.

The tower that collapsed Wednesday was the last of six on the church that had been filled with mortar in recent days.

“We were almost done,” Brown said. “You get down to the last one, you think it’s time for celebrating.”

As far as what exactly went wrong, “We’re not really sure what happened at this point,” said Frank Halsey, president of Mid-Continental Restoration Co. of Fort Scott, the company that was doing the work.

“We’re not sure if there was a structural defect at the base where it blew out,” he said. “We know that there had been some work there that had been done previously.”

Halsey said his workers were following guidelines set by Don McMican, a Kansas City area engineering consultant hired by the church. He said he was “very confident” in the stability of the other five towers that had been filled.

Brown said he didn’t want to assign blame for why the tower fell and that it’s possible it was weakened during last year’s storm.

“We did everything humanly possible we could do” to vet the project ahead of time, Brown said.

He said the issue of who would pay the tab for the repair effort was still being settled Thursday, and that insurance companies would be involved.

The Rev. Peter Luckey said the congregation has been generous so far in helping repair storm damage to the 137-year-old building. Rebuilding the two towers that fell in last year’s storm cost about $60,000.

“It’s an old building. It takes a lot of money to maintain,” Luckey said.

The church had to cancel a noon service for Thursday but reopened in time for an evening service.