Bill Chappell

The Federal Trade Commission is in the early stages of opening an antitrust probe into how Google runs its online display advertising business, according to a report by Bloomberg News, citing sources who want to remain anonymous because the FTC has not announced the probe.

Populations of frogs, salamanders and other amphibians are declining at an average rate of 3.7 percent each year, according to a U.S. Geological Survey study released this week. Researchers say the study is the first to calculate how quickly amphibians are disappearing in the United States.

"If the rate observed is representative and remains unchanged, these species would disappear from half of the habitats they currently occupy in about 20 years," according to the USGS.

Residents of Moore, Okla., are searching for survivors and coming to terms with a massive tornado that left dozens of people dead and injured more than 200 others Monday afternoon. As aid and recovery groups search for victims and try to reunite loved ones, they're also seeking donations and coordinating housing:

A scholarly publisher has issued a warning to Jeffrey Beall, a librarian who writes about what he calls "predatory" practices in the scholarly publishing industry, threatening him with a $1 billion lawsuit for his blog posts criticizing the company.

Beall is an academic librarian at the University of Colorado; he writes about the journal industry on his personal blog, Scholarly Open Access.

Colorado is set to become the first U.S. state to regulate and tax sales of recreational marijuana, after lawmakers approved several bills that set business standards and rules. Legislators expect enforcement of the rules to be paid for by two taxes on marijuana — a 15 percent excise tax, and a 10 percent sales tax.

Other measures included in the package set limits on how much marijuana visitors to Colorado can buy (a quarter of an ounce), as well as a limit on how many cannabis plants a private citizen can grow (six).

Israeli warplanes attacked a military research center near Damascus early Sunday, according to intelligence reports and Syrian state media. The attack prompted Syrian Deputy Foreign Minister Faisal al Mekdad to deem it a "declaration of war" by Israel, CNN reports.

Federal agents who are investigating poison-laced letters that were sent to President Obama and others have arrested Everett Dutschke, of Tupelo, Miss. The Daily Journal of Tupelo reports that the arrest occurred around 1 a.m. Saturday.

In addition to the president, letters containing the poison ricin were sent to Sen. Roger Wicker and a Mississippi state judge.

Update at 11:55 a.m. ET. Charges Filed, Court Date Set

Towns in Missouri, central Illinois and at least four other Midwestern states are under a flood warning, as heavy spring rains swell the Mississippi and other rivers to dangerously high crests. In some areas, rivers have already hit record flood levels.

In places where residents have been forced to evacuate their homes, the American Red Cross has set up shelters at schools and other facilities.

Boston bombing suspect Dzhokhar Tsarnaev has not yet been questioned — but officials' decision not to read him his Miranda rights before interrogation is the subject of much debate.