A York County couple pleaded guilty Friday in U.S. District Court in Columbia to making and mailing explosive devices in a somewhat elaborate scheme to have law enforcement investigate people they had quarrels with, according to federal prosecutors.

Christopher Gilberto and his wife, Cruz De Jesus Gilberto, each pleaded guilty to multiple charges of aggravated identity theft, manufacturing an explosive device, and two separate conspiracies related to the mailing of explosive devices in South Carolina and North Carolina.

According to the U.S. Attorney's Office in Columbia, the federal investigation began in February 2005 when a package containing an improvised explosive device was found at a Rock Hill restaurant and three additional improvised explosive devices were mailed to financial institutions and private citizens in York County in 2006 and 2007. Authorities said several threatening letters also were mailed to financial institutions and the Federal Bureau of Investigation's Charlotte office.

One of those letters told the FBI a bomb would be detonated at Charlotte- Douglas International Airport in Charlotte at 9:11 a.m. in March 2007. That letter prompted an "exhaustive effort" to learn the identity of the letter writer, authorities said.

Federal agents subsequently arrested the Gilbertos and searched their home on March 9, 2007.

Agents found numerous items linking the Gilbertos to the explosive devices and the letters, including the typewriter ribbon that bore the impressions of the letter mailed to the FBI, according to the U.S. Attorney's Office.

Authorities alleged the Gilbertos were motivated by disagreements they had with several victims in the case, including the owner of the Rock Hill restaurant who decided not to renew a contract with Gilberto for window cleaning services.

Authorities said the names of people who worked with Cruz Gilberto had been placed in the return addresses of the explosives sent through the mail in an apparent attempt to have those people investigated by federal agents.

Sentencing for the Gilbertos will be held at a later date.

Tim Gulla