U.S. safety regulators have upgraded an investigation into almost 387,000 Jeep Liberty sport utility vehicles for potential inadvertent airbag deployment, increasing the possibility of a recall.

The National Highway Traffic Safety Administration said it was upgrading its investigation of the 386,873 Chrysler SUVs from model years 2002 and 2003 to an engineering analysis, a step in a process that could lead to a recall if regulators determine that a manufacturer needs to address a safety issue.

In two separate other NHTSA filings, Mazda Motor Corp Motor Corp is recalling more than 52,000 older Tribute SUVs for potential brake fluid leaks, and Daimler AG's Mercedes-Benz has begun investigating consumer complaints of fuel odor that may be a leak in about 8,000 older E55 AMG sedans and wagons.

For the Chrysler issue, NHTSA said it had identified 87 reports of inadvertent driver or passenger front airbag deployment, resulting in 50 alleged injuries, including burns, cuts and bruises to the upper body, according to documents filed online.

Forty-two of the 87 incidents involved the driver front airbag deploying without a crash, occurring at vehicle startup and while driving on the road, according to NHTSA. The remaining 45 involved both the driver and passenger front airbags, NHTSA said.

Some drivers noted that the airbag warning light had illuminated just prior to airbag deployment, while others did not observe one, NHTSA said.

An inspection conducted by Chrysler indicates an internal electronic chip that controls airbag deployment failed, possibly due to a voltage spike. The automaker, which is controlled by Fiat, is in the process of identifying possible root causes, NHTSA said.

NHTSA initially opened a probe into the Jeep SUVs in September after receiving seven consumer complaints.

A Chrysler spokesman said the U.S. automaker was cooperating with the investigation.

In separate documents, NHTSA said Mazda is recalling more than 52,000 Tribute SUVs for potential brake fluid leak that could lead to a fire.

Mazda is notifying owners this week of 52,390 Tributes from model years 2001 and 2002 about the potential brake fluid leaks that could come into contact with the anti-lock brake system module wiring harness, according to documents NHTSA.

A Mazda spokesman said no injuries or accidents have been reported related to this issue.

In the case of a leak, corrosion could develop and lead to melting, smoking or fire, according NHTSA.

The affected vehicles were built at Ford Motor Co Kansas City Assembly Plant in Missouri, according to NHTSA. Until the repairs are made, owners are being told to park their vehicles outside, according to NHTSA.

The Mercedes-Benz issue covers about 8,100 E55 AMG sedans and wagons in model years 2003-2006.

NHTSA documents show that 20 consumers have complained about the odor of gasoline inside or outside of the car. Several of them suggested the issue may be related to a 2008 recall that involved possible cracking of a fuel filter module in vehicles exposed to high ambient temperatures.

(Reporting by Ben Klayman and Bernie Woodall in Detroit; Editing by Lisa Von Ahn)