All it takes to set curators of area historical societies and museums on edge are three words:

The Ortiz Brothers.

An alert this week about the movements of Michael Ortiz, 40, and his brother Roy, 37, who previously admitted they were responsible for hundreds of thefts from small museums where historical artifacts are displayed, has officials warning each other to be on the lookout and to take steps to protect their collections.

“They are definitely out and about,” Melissa Dunlap, executive director of the History Center of Niagara County, said Friday.

One of the brothers was spotted last Saturday at the Lockport center. Michael Ortiz was seen Oct. 19 at the Landmark Society in Rochester. Prior to that, Michael and his Roy were observed at the Greece Historical Society in that Rochester suburb. Officials at the Fenton Historical Society in Jamestown reported spotting a man believed to be one of the brothers on Oct. 23.

“We’re trying to get the word out to all the historical venues where there would be [historical] items of value that might be vulnerable,” said Donna Zellner Neal, executive director of the North Tonawanda History Museum. But the fact that Michael Ortiz, whose last known address was in Medina, revisited the history center is more than upsetting, she said.

“I think it is extremely bold,” she said.

If history is any guide, the officials say they have reason to be concerned.

When the brothers were arrested in 2006, they admitted to hitting 200 to 500 sites during an 18-month stealing spree, using a tourism map of 112 venues in New York and northern Pennsylvania, investigators said then. Many of the stolen items were sold on eBay.

“In 2006, the brothers stole two irreplaceable Presidential Medals from us belonging to Ely S. Parker, the Seneca and secretary to General [Ulysses S.] Grant," said Dunlap. “Parker wrote the terms of the surrender of the South at Appomattox.”

The medals, worth thousands of dollars, were recovered, Dunlap said.

In 2010, Michael Ortiz was arrested and charged with stealing an antique revolver from the West Seneca Historical Society. The weapon was believed to be owned by a man who might have been a member of the Jesse James Gang and had spent the balance of his life in West Seneca. Roy Ortiz was arrested that same year for a burglary at a museum in the Finger Lakes.

Neal said her staff will soon be equipped with whistles.

“We have 10,000 square feet of exhibit space and if anyone hears a whistle go off, they’ll know that one of the Ortiz brothers has been spotted in the building,” Neal said.

The brothers, according to historical facility officials, have a specific method of operation. In the past, they were known to send in a person to scout out things that would be of interest, and later the same day they would show up themselves and attempt to steal the items.

“One of the brothers will come in and attempt to distract a staff member while the other tries to steal,” Neal said.

The Western New York Association of Historical Agencies has sent out a bulletin that quoted a staff member at the history center in Lockport:

“A man who looked very much like the photo of Michael Ortiz stopped in [at the History Center of Niagara County on Nov. 3] at 4:40 p.m. to ‘check out the building before bringing his sons next week.’ He signed in as ‘Todd Kelso.’

“He asked about the hours. I showed him the main building. He was particularly interested in the Civil War exhibit. He is about 5’5” or 5’6” and has a rather high-pitched voice. He left in a metallic blue Chevy sedan …”

The staffer, Dunlap said, got the license plate number and police confirmed the vehicle belonged to Michael Ortiz.

Terry C. Abrams, administrative coordinator for the historical agencies association, suggested that museums and other sites have more than one person on duty when the location is open.