April 17 (Bloomberg) -- Smoke from fires set by farmers to clear fields for grazing covered the city of Buenos Aires and shut down some highways leading into the Argentine capital.

Interior Minister Florencio Randazzo called the smoke a ``disaster'' and said 292 separate fires covering 70,000 hectares (173,000 acres) had been detected in the provinces of Buenos Aires and neighboring Entre Rios.

Farmers are burning more land as they create pastures for cattle that previously grazed fields now dedicated to soybeans, said Randazzo. An 89 percent increase in soybean futures prices in the past year, part of a global explosion in food costs, has prompted Argentine farmers to increase the area sown to the oilseed by 10 percent, according to the Agriculture Secretariat.

``Those responsible are farmers who are burning their meadows to cut costs and maximize profits without considering the consequences,'' said Randazzo in a news conference at the Presidential Palace. ``We are conducting investigations to find those responsible.''

The burning of land is an annual occurrence in the Argentine countryside and the Parana River delta.

In the capital, the smell of smoke filled homes and offices. Views of landmarks, including the downtown Obelisk and the Defense Ministry building, were clouded.

`Unbreathable'

President Cristina Fernandez de Kirchner, who said she smelt the smoke when she left her office last night, criticized the farmers' actions.

``Yesterday, the air in Buenos Aires was unbreathable, people's eyes burned and the smoke infiltrated our clothes,'' Fernandez said in speech at the opening of a factory in Buenos Aires province. ``I'm calling on those who work in the countryside to act responsibly.''

Randazzo said tests indicated there was a high level of carbon monoxide in the air. On its early morning show, Radio Mitre received calls from dozens of people complaining of eye irritation and sore throats.

``I'm thinking of getting out of here for the weekend if this smoke continues,'' said Stafford McCay, 25, a U.S.-born businessman who lives in Berlin and is visiting Argentina. ``Several people in my party have experienced headaches and stinging eyes.''

McCay said he may go to neighboring Uruguay until the situation in Buenos Aires improves.

Television channels showed helicopters scooping water from the Parana River and dumping it on blazing islands in an effort to douse flames.

Carbon Monoxide

Tests conducted this morning by doctors from the Hospital de Clinicas in Buenos Aires showed that some people had four times the normal level of carbon monoxide in their lungs, said doctor Ricardo Gene in a telephone interview.

``The smoke may worsen pre-existent illnesses such as asthma and other respiratory problems,'' Gene said.

The port of Buenos Aires was closed for shipments to the north, while the city's main bus terminal didn't allow departures of buses destined for northern provinces, Randazzo said.

``Covering highways with smoke just to clear a field of weeds is unforgivable,'' Cabinet Chief Alberto Fernandez said an interview with Radio Diez. ``It's incredibly irresponsible.''

Environment Secretary Romina Picolotti and Randazzo this afternoon will meet provincial governors to discuss what further measures should be taken.

The national meteorological service issued an alert saying cloud banks caused by the smoke would reduce visibility. The service forecast light winds that may ``temporarily'' clear smoke.

``The good news is that in the next 24 hours there will be some southeast winds that will minimize the smoke in populated areas and help increase visibility on roads,'' said Picolotti, who spoke at the same press conference as Randazzo.

To contact the reporter on this story: Bill Faries in Buenos Aires wfaries@bloomberg.net; Eliana Raszewski in Buenos Aires eraszewski@bloomberg.net

Last Updated: April 17, 2008 15:21 EDT