BALTIMORE - The American Civil Liberties Union is accusing the Baltimore Police Department of using invasive surveillance technology.

The ACLU claims the police are violating people's privacy in a way that's intrusive and illegal by tapping into their cell phones using a device called "Stingray," reports CBS Baltimore.

"Stingray" is a small portable device that mimics a cell phone tower, forcing all cell phones within range to connect, allowing access to cell records, text messages and even the precise location.

Get Breaking News Delivered to Your Inbox

The ACLU says the cell phone surveillance gear violates the Fourth Amendment, which protects people from unreasonable searches by the government.

"We think it should not be used by police in Baltimore or anywhere else without a warrant," said David Rocah, a senior staff attorney for the ACLU.

The ACLU filed a brief, challenging the Baltimore Police Department's use of "Stingray," arguing it is deceptive.

In a pending criminal case, Baltimore police used a "Stingray" to zero in on a person's home, but did not get a warrant. Instead, they obtained a special court order that required less than probable cause.

The ACLU believes it's misconduct and also a violation of people's rights since it also collects innocent people's information without their consent.

Reactions by Marylanders to CBS Baltimore about the police practice were mixed.

"I don't have a problem with that, as long as the purpose of collecting is legitimate," said Paul Kelly.

"Law enforcement isn't full of good people so it's a tough thing to know how to balance that out," said Matthew Anderson.

"If we weren't already giving up our information, Apple has all of your cell phone tracking data. I trust the police more than I do a corporation. So I'm comfortable with it," said July Kelly.

The ACLU alleges police have been told not to release basic information about the "Stingray" operation.

"The question needs to be asked: what exactly are police and the manufacturer trying to hide?" Rocah said.

The ACLU claims that 47 agencies and 19 states are using the device "Stingray."

The Baltimore police have declined to comment on this matter.