A rejected shipment of the highly toxic chemical methyl isocyanate was unloaded under heavy security but without incident at Norfolk International Terminals early today, then was trucked safely to Georgia in an extraordinary convoy.

Brazil had rejected the 13-ton shipment and ordered it returned to its American manufacturer, Union Carbide Corp., after leaking MIC killed at least 2,000 people at the company's plant in Bhopal, India, in the worst industrial accident in history.

The cargo had been packed in the sixty-eight 55-gallon stainless steel drums at the Carbide plant in Institute, W.Va., and shipped to Brazil in late November, shortly before the Dec. 3 leak in India. The chemical is an intermediate compound of the carbamate class that is used in the production of about one-third of the world's pesticides.

The company tried to play down the significance of today's event, noting that MIC produced in Institute -- the only place in the United States where it was made -- has been shipped through the port here about four times a month for the last 10 years.

But the activity here, and along a 625-mile land route to Union Carbide's plant in Woodbine, Ga., where the chemical will be turned into pesticide, was anything but ordinary.

At 3:30 a.m., a Coast Guard vessel pulled aside the United States Lines freighter American Rigel as it entered the Hampton Roads waterway at Cape Henry, the last leg of the MIC's return trip from Rio de Janeiro.

Two security officers were put aboard, and by the time the American Rigel tied up at Pier CB-1 at 5:50 a.m., Coast Guard Lt. George Matthews and Chief Warrant Officer Terry Holub had determined there were "absolutely no problems" with the two 20-foot trailers, each containing 34 drums filled with the chemical in liquid form.

Union Carbide safety experts opened the trailers and inspected their packing before placing them on truck beds. Virginia state police then inspected them, and the two trucks were ready to leave the port.

A caravan that included a Union Carbide car carrying safety and public relations officials and state police and highway patrol cruisers -- trailed by reporters and photographers in cars or hovering in helicopters -- escorted the two trucks along Interstate Rte. 95, creating traffic backups by driving in the passing lane while police barred other vehicles from passing.

At 11:00 p.m., the trucks arrived at Union Carbide's Woodbine plant, just north of the Florida border, to a scene of television cameras and state police similar to the one that greeted the shipment in Norfolk.

Mary Anne Ford, a Union Carbide spokesman who rode in the convoy, said the trip went off "without a hitch."

During a lunch break at a truck stop in North Carolina, a driver of one of the trucks, Donald Dirickson, said, "The most dangerous part of the trip was when all of those TV vans raced out of the port following us."

Department of Transportation regulations require that trucks carrying hazardous cargo be so marked and stop every 100 miles to inspect their tires, which the convoy did at rest areas and along the berm.

But there are no laws requiring non-nuclear hazardous cargoes to file itineraries or to be escorted. North Carolina Highway Patrol Lt. W.H. Long said the trucks were being "monitored, but not escorted," by patrol cars.

Regulations published by Union Carbide tell drivers transporting MIC to "avoid congested routes; bypass cities and towns; make as few stops as possible."

The driver information packet adds, "do not open the trailer for inspection or for any other reason. If a leak is suspected, drive the truck to an isolated area near a source of water, preferably pressurized. Notify the nearest fire department so a pumper truck can be made available if needed. Phone the HELP hazardous emergency leak procedure number and your dispatcher."

The four drivers taking turns at the wheel today all were from West Virginia and had experience transporting MIC from the plant there, although the route was new to them.

MIC ordinarily is shipped by rail or truck to the port in Norfolk or to the Georgia plant directly from Institute. (All MIC production has been stopped by Union Carbide until completion of the investigation of the accident in India.)

Carl Franson, the ship's navigation officer, said U.S. Lines "did everything by the books." He said he didn't believe any of the 43-member crew thought there was "any hazard at all." Franson, 29, said he worked on tanker ships for five years and "they pose much more of a threat than those two containers."

The containers were bolted down on hatch 10 on the deck. Franson said hazardous cargo is always carried on the deck "in case it has to be jettisoned."

Lt. Cmdr. Fred Brox, a Coast Guard spokesman, said the inspectors "rode the vessel in . . . to expedite the inspection process, . . . because you guys the news media are here and to put the public's mind at rest" that the dangerous cargo had survived the voyage safely.

Ordinarily, ships are inspected semi-annually, after they have docked. The American Rigel was due for a routine six-month check, Brox said.

A second shipment of MIC, rejected by France, is scheduled to arrive in Norfolk on Jan. 8, aboard a Danish freighter.