This story was updated May 4 at 4:35 p.m. to include comment from Immigration and Customs Enforcement.

The Department of Homeland Security has scaled back the scope of contractor requirements for what would have been a nationwide license plate-scanning effort, amid continued uproar over the on-again-off-again project.

The new system, announced last month, will compile license plate records from "at least 25 states" instead of all states, DHS Immigration and Customs Enforcement officials said in a May 1 modification of the contract requirements. Officials later told Nextgov relaxing the requirements would allow more companies to compete for the job.

More than a year ago, DHS Secretary Jeh Johnson cancelled a similar plate-tracking project after concerns were raised that plate data-searching tools essentially amounted to location-tracking technology.

ICE officials say the service is intended to help apprehend immigrant fugitives, along with individuals suspected of child pornography, illegal arms exports and other illegal activity.

Under the revised plan, the number of records supplied monthly by the contract would also decrease. The modified contract says the vendor must supply at least 6 million records per month, replacing April specifications that at least 30 million records be available.

The number of metro areas under surveillance also will be somewhat restricted. Rather than compiling plate data from 30 metro areas, the vendor will aggregate data from 24 metro areas.

License-plate recognition companies index images of plates from surveillance cameras at toll roads, parking lots and other locations across the country, in part, to help authorities track the movements of suspects.

The ICE service will scour for "known license plate numbers associated with the aliens who are immigration enforcement priorities” and track “where and when the vehicle has traveled within a specified period of time,” government officials say.

Homeland Security maintains the service will not create a repository of license plate data, but instead create a mechanism to search separate databases maintained by private companies and government agencies.

"ICE is neither seeking to build nor contribute to any public or private" database, officials said in a solicitation for vendors issued April 17. The purpose of the contract is to provide authorities round-the-clock access to "a commercially available, query-based" license plate database for ICE law enforcement personnel.

Early in April, indications surfaced that last year’s nixed project was making a comeback, with the publication of a privacy impact assessment describing how ICE "intends to procure the services of a commercial vendor of [license plate reader] information."

The American Civil Liberties Union and other public advocacy groups still view the service as akin to having Big Brother in the passenger seat.

"It's appropriate to use license plate scanners to check for wanted vehicles, but the technology should never be used to store up databases of the movements of vehicles that are not on any hot lists," ACLU senior policy analyst Jay Stanley and ACLU legal assistant Bennett Stein wrote in an April 6 blog entry. "It violates the longstanding tenet that the government not monitor citizens unless it has individualized suspicion of involvement in wrongdoing."

On Friday, Virginia Gov. Terry McAuliffe vetoed legislation that would have restricted the time period authorities can store data from license plate readers, according to The Washington Post.

"In siding with police and prosecutors," McAuliffe argued the measures "would have added unintended burdens to fighting crime," The Post reported.

Three years ago, ICE was poised to ink a sole-source contract with license plate-tracker Vigilant Video that would have provided more than 685 million continually updated images of plates, Nextgov reported at the time.

The system was aimed at helping field personnel pinpoint the whereabouts of escaped undocumented immigrants. Five days later, the agency abandoned the deal, saying another unnamed vendor came forward claiming to sell the same vehicle-tracking services. The agency never identified the second company.

Proposals for the new contract are due by the end of the day Wednesday.

Late Monday afternoon, ICE officials said they reduced the the amount of information contractors must assemble to lower the bar for interested, but less data-rich companies. Depending on which contractor wins, it seems the data collection might actually grow.

“ICE modified the solicitation based on feedback from vendors requesting that the minimum threshold for records be lowered in order to facilitate greater competition," agency spokeswoman Gillian M. Christensen said in an email. "ICE has not scaled back the scope or protections. We have lowered some of the minimum requirements to allow additional commercial vendors to participate in this acquisition.”