Sunday's fire, which happened when the congregation was away at a church picnic, took more than two hours to knock down and left the nearly century-old stone structure with significant damage.
The ATF is looking into the blaze with the city Fire Marshal's Office because the fire involved an active place of worship, Bartholomew said. The ATF's presence does not necessarily indicate criminal wrongdoing, he added, although investigators did not know whether the fire was accidental, an act of nature, or deliberate.
While investigators were scratching for clues, others were dealing with what to do next.
Mechanical shovels reached into the house of worship at 12th Street and Oak Lane Avenue to remove debris, and workers from the city demolition contractor Gama Wrecking used excavators to shovel out charred rubbish from inside the shell. Barricades and police sealed off the scene.
Meanwhile, church leaders met in the rectory behind closed doors to discuss plans. No announcements were made.
Nearby St. Vladimir Ukrainian Orthodox Cathedral is assisting St. Mary in its time of need.
St. Vladimir Pastor Taras Naumenko said his church, blocks away on Fifth Street, would host a joint service of the two congregations starting at 9:30 a.m. Sunday.
Beyond Sunday, Naumenko said, his church will offer worship space to St. Mary parishioners, and logistics need to be worked out on how St. Mary parishioners could hold services at St. Vladimir.
Both churches have discussed merging because of declining membership.
Contact Sulaiman Abdur-Rahman at sabdur-rahman@phillynews.
com, or follow on Twitter @sabdurr.