Boston Mayor Marty Walsh said he didn't force out the head of the Boston Public Library, but noted Monday that he learned from a FOX 25 reporter that more items were missing from the Boston Public Library.

A listener email to WGBH's "Boston Public Radio" pointed to Walsh "harshly" criticizing Amy Ryan, who started as Boston Public Library president under the late Mayor Thomas Menino and last week announced plans to resign effective July 3, for not reporting missing items to him, according to co-host Margery Eagan.

A day after Ryan said she would resign, library officials announced that they had found the missing art pieces 80 feet away from where they should have been filed. The two items were an engraving by Albrecht Durer, which has an estimated value of $600,000, and a Rembrandt etching estimated to be worth between $20,000 and $300,000.

"You know, I'm very happy that we found the pieces," said Walsh, appearing on the program as part of a regular "Ask the Mayor" segment. "But this goes back to [the] 2012 audit that spelled out that we have a problem with safety, security at the library. This is prior to me becoming mayor of the city of Boston. That audit was not addressed."

Walsh said last week a FOX 25 reporter interviewed him after library officials announced music sheets were missing and it was the first he had heard about the news. "As mayor of the city of Boston, I think I should know before that," Walsh said. "A lot of these things have a value on them but they're really priceless. Amy resigned on her own."

He added: "If this was the [Boston Redevelopment Authority], people would be berserk about it," he said. "If this was public health, people would be berserk about it."

Library officials last week said they plan to complete a safety and security plan by the end of July 2015 and expand the management of its collections.

According to the library, Dr. Martha Mahard, a preservationist, has started an inventory of 200,000 prints and drawings, as well as 120,000 chromolithographs. The inventory is expected to be finished by the end of 2015.

"We shouldn't have lost a 600,000 dollar print that dates back to, I think, 16-something," Walsh said on Monday. "This isn't right."

In a statement last week, Ryan said, "I am choosing to step aside at this time to allow the work of the Boston Public Library to continue without distraction."

"I believe as strongly in the mission of the Boston Public Library today as when I arrived from Minnesota nearly eight years ago," she added. "I am honored to have contributed to the success of a public library system that is truly free to all and unswervingly committed to serving people of all ages and from all walks of life throughout the City of Boston and the Commonwealth."