The shroud is a strip of linen believers say was used to wrap the body of Jesus. Kept in the Cathedral of Turin, it is rarely displayed to the public.
Earlier this month, the Rome newspaper Il Messaggero said a well-known Swiss textile expert, Mechthild Flury-Lemberg, had begun tests on the cloth and, as part of the research, cut out 30 patches woven into it in the 16th century.
Flury-Lemberg confirmed then that she had received Vatican approval to perform the tests. But she has refused to say exactly what her work has entailed.
Some experts worry that in the absence of any oversight, she may have damaged the cloth. In the past, tests on the cloth have involved a large committee of international scientists.
"This one was limited strictly to certain favorites in Turin, and Flury-Lemberg was one," said the Rev. Albert Dreisbach, an Episcopalian minister who has been studying the shroud since 1977.
Flury-Lemberg said Wednesday she would release photographs of her research next month.
"There are so many wrong things in the press," she said by telephone from Bern, Switzerland. "Everyone's speculating. I don't want to give any news."
Cardinal Severino Poletto, the archbishop of Turin and the shroud's custodian, said in an interview with the Italian Catholic newspaper L'Avvenire that the Vatican approved the tests.
He would not discuss Flury-Lemberg's procedures except to say her work was carried out in accordance with two Vatican conditions: that there be unanimous consent of the members of the Conservation Commission for the Shroud, a small group of experts overseeing the cloth, and that the cultural authorities of the Italian government be informed.
Members of the commission could not be reached Wednesday.
Ilona Farkas, who has been following shroud research since 1976 but
is not a commission member, said scientists are upset.
"It's scandalous," Farkas said from Rome. "There will be tons of protests arriving at the Vatican from scientists."
Paul Maloney, general projects director for the Association of Scientists and Scholars International for the Shroud of Turin, located in Pennsylvania, said the lack of information has "many of us around the world very frustrated, because we don't know how to assess what they have done."
Maloney, who is also not a member of the smaller commission, said experts fear "historically important information may be gone forever."
The cardinal said the research involved removing impurities and residue from the cloth, which is 13 feet long and three feet wide.
"The interventions have been carried out reservedly not out of a great desire for secrecy, but to guarantee the necessary calm for those who had to work, beside obvious reasons for safety," Poletto told L'Avvenire.