U.S. lawmakers have asked the Environmental Protection Agency (EPA) to explain why it published - and then withdrew - documents related to its review of glyphosate, the chemical in Monsanto Co's Roundup herbicide, according to a letter seen by Reuters.

The documents, which included a report that said glyphosate is not likely to be carcinogenic to humans, were posted by the EPA on April 29 and taken down from a website the government agency manages on May 2.

The letter, sent from the agriculture committee of the U.S. House of Representatives, marks the latest salvo in an ongoing debate over the EPA's role and influence in U.S. agriculture.

According to the letter, which cites a May 2 story by Reuters, the committee is looking into the EPA's recent actions related to the agency's multi-year review of potential risks tied to glyphosate and atrazine, another popular chemical used in agricultural herbicides.

The documents are part of the EPA's registration review of glyphosate and its potential human health and environmental risks, which started in 2009.

"We are troubled that EPA mistakenly posted and later removed documents related to assessments of two different chemicals within one week," according to the letter, signed by the Republican and Democrat leaders of the committee.

"These mistakes indicate systemic problems with EPA's management of its chemical review and publication processes."

The letter was sent to the EPA on Wednesday. The committee, which is conducting an oversight into the EPA's recent actions, will consider what action to take after it receives a response from the agency.

The EPA told Reuters on Thursday the agency has received the letter "and will respond appropriately."

The letter also asked the EPA who is in charge of overseeing the risk assessment process for chemicals and for a step-by-step description of the agency's approval process for publication of such assessments.

The committee also wanted to know what steps still needed to be taken to finalize and issue the glyphosate report, which it had expected in July 2015.

"We are concerned that EPA has continually delayed its review of glyphosate," the letter said.

On April 29, the agency posted a series of documents, including a report marked "FINAL" from the EPA's cancer assessment review committee (CARC). That report found that glyphosate, the active ingredient in the world's mostly widely used weedkiller, was "not likely to be carcinogenic to humans."

Another document also published on the regulations.gov website that the EPA manages and pulled down on May 2, was a preliminary assessment of the ecological risks of atrazine. Among other things, the report stated that atrazine effects exceeded EPA's "levels of concern" for chronic risk by 198 times for mammals, and 62 times for fish.

At the time, the agency told Reuters it took down the glyphosate report and other documents "because our assessment is not final." The agency said the documents were "preliminary" and that they were published "inadvertently."