PHOENIX - The company that owns a luxury jet that crashed and killed singer Jenni Rivera is under investigation by the U.S. Drug Enforcement Administration, and the agency had seized two of its planes this year as part of the probe.

DEA spokeswoman Lisa Webb Johnson confirmed Thursday that the planes owned by Las Vegas-based Starwood Management were seized in Texas and Arizona, but she declined to discuss details of the case. The agency also has subpoenaed all of the company's records.

The man widely believed to be behind the aviation company is an ex-convict named Christian Esquino, 50. Corporate records list his sister-in-law as the company's only officer, but insurance companies that cover some of the firm's planes say in court documents that the woman is merely a front and that Esquino is in charge.

Esquino's legal woes date back decades. He pleaded guilty to a fraud charge that stemmed from a major drug investigation in Florida in the early 1990s and most recently was sentenced to two years in federal prison in a California aviation fraud case. Esquino, a Mexican citizen, was deported upon his release. Esquino and various other companies he has either been involved with or owns have also been sued for failing to pay millions of dollars in loans, according to court records.

Rivera, 43, a Califiornia native, died at the peak of her career when the plane nose-dived while flying from the northern Mexican city of Monterrey to the central city of Toluca early Sunday. She was perhaps the most successful female singer in grupero, a male-dominated Mexico regional style, and had branched out into acting and reality television.

It remained unclear Thursday what caused the crash and why Rivera was on Esquino's plane. The pilot and five other people were also killed.

Esquino told the Los Angeles Times in a telephone interview from Mexico City that the singer was considering buying the aircraft from Starwood for $250,000 and the flight was offered as a test ride. He disputed reports that he owns Starwood, maintaining that he is merely the company's operations manager.