(CNN) -- U.S. Attorney General Eric Holder said Tuesday the Justice Department has launched a criminal investigation into the massive oil spill spreading through the Gulf of Mexico.





Holder said the investigation, which began "some weeks ago," would be comprehensive and aggressive. He promised that the federal officials will prosecute anyone who broke the law.





"We have begun both a criminal as well as a civil investigation as is our obligation under the law," Holder said. "We have what we think is a sufficient case to have begun a criminal investigation."





Holder emphasized that the investigation will cover all aspects of the oil spill, including the deaths of 11 workers in the April 20 explosion and fire on the Deepwater Horizon rig that started the leak.





He refused to name any potential targets of the investigation, saying, "I don't want to unnecessarily cast aspersions." However, Holder said "nothing is off the table" in the probe, and he cited false statements as one of several potential targets of criminal charges.





"This disaster is nothing less than a tragedy," Holder said. "As our review expands in the days ahead, we will be meticulous, we will be comprehensive, and we will be aggressive. We will not rest until justice is done."





Holder stressed that "anyone found responsible for this spill (must be) held accountable. That means enforcing the appropriate civil -- and if warranted, criminal -- authorities to the full extent of the law."





Among other things, Holder said Justice Department lawyers are examining possible violations of the Clean Water Act and the Oil Pollution Act of 1990. He also said prosecutors are looking into potential violations of the Migratory Bird Treaty and Endangered Species Acts, which provide penalties for injury and death to wildlife.





BP responded in a statement that it "will cooperate with any inquiry the Department of Justice will undertake, just as we are doing in response to the other inquires that are already ongoing."





Holder made the announcement during a visit to the Gulf to survey the BP oil spill and meet with state attorneys general and federal prosecutors from Louisiana, Alabama and Mississippi, according to the Justice Department.





Last month, a group of senators -- including Environment and Public Works Committee Chair Sen. Barbara Boxer, D-California -- sent Holder a letter expressing concerns "about the truthfulness and accuracy of statements submitted by BP to the government in its initial exploration plan for the site." They asked the attorney general to investigate possible criminal and civil wrongdoing.





In a reply to that letter last week, a Justice Department official refused to say whether a criminal investigation had begun.





"The Department of Justice will take all necessary and appropriate steps to ensure that those responsible for this tragic series of events are held fully accountable," Assistant Attorney General Ronald Welch wrote.





Holder said last month the Justice Department would "ensure that BP is held liable."





Boxer issued a statement Monday praising the criminal probe.





"In preparation for the Environment Committee's hearings on the oil spill, it became clear that BP's assurances that they could respond effectively to a serious spill at this site were totally at odds with reality," Boxer said in the statement. "What is happening in the Gulf -- eleven people dead, and an entire ecosystem and the jobs that depend on it at risk -- justifies a thorough criminal investigation."





CNN's Scott Bronstein and Aaron Cooper contributed to this report
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