BALTIMORE (REUTERS) - A former security officer at a federal laboratory in Maryland pleaded guilty on Friday to trying to make methamphetamine at work last month, setting off an explosion in what his lawyer has described as an unauthorised experiment.

Christopher Bartley, 41, of Gaithersburg, Maryland, pleaded guilty in US District Court to one count of attempting to make the drug while working at the National Institute of Standards and Technology (NIST), also in Gaithersburg.

The charge stemmed from a July 18 explosion in the NIST laboratory.

Bartley resigned the next day, according to an agency spokeswoman.

"Methamphetamine is unsafe to produce and unsafe to use," said US Attorney Rod Rosenstein in a statement.

"Bartley damaged government property and jeopardised the health and safety of NIST employees by mixing dangerous chemicals."

Prosecutors said that Bartley's attempt to make the drug caused an explosion that blew out four shatterproof windows in the lab where he was working and raised the temperature inside to 82 deg C, triggering a silent heat alarm.

Bartley fled the building, disposing of items in a dumpster at that location and near another nearby lab run by the same agency, they said.

Law enforcement agents later searched the trash near those facilities and seized a number of items used in manufacturing the drug, including a coffee grinder with white powder residue, rubber gloves, a gas mask and protective safety glasses.

Law enforcement agents also searched Bartley's vehicle and recovered a book that contained his handwritten notes of ingredients and equipment needed to make methamphetamine.

He later admitted to a federal agent that he had been trying to make the drug, prosecutors said.

Less than 5g of methamphetamine was involved.

Bartley, who is not in custody, faces a maximum sentence of 20 years in prison. Sentencing is scheduled for Nov 19.

Bartley's attorney, Steven VanGrack, earlier this week described his client as a "distinguished" military veteran who was conducting "an unauthorised training experiment that failed".