A Howard University professor who specializes in black Latin American literature has spent the last three weeks imprisoned in his native Grenada for allegedly plotting to overthrow the government of the southern Caribbean island.

Stanley Cyrus, who relatives say was visiting Grenada on academic leave to visit his blind, 75-year-old father, was arrested at 5 a.m. on Oct. 15 and taken to Richmond Hill Prison in St. Georges for questioning. o

Dessime Williams, Grenada's ambassador to the Organization of American States in Washington, D.C., said yesterday through a press officer that Cyrus would be charged for his alleged role in the attempted coup, along with dozens of others arested in recent weeks.

The arrests, said Grenada's ambassador to the United States, Kendrick Radix, broke the back of an attempt to overthrow the eight-month-old leftist government of Prime Minister Maurice Bishop with a force of "100 foreign mercenaries," and opposition party members who Radix said were trying to assassinate government officials.

Cyrus' sister, Christobel Riddick, a Houston nurse who visited the Howard professor last Friday in Grenada, said he was baffled by the sudden arrest.

"He said, 'Chris, I don't know why they picked me up. I haven't done anything. But if they can arrest me without cause, they can do anything,'" Riddick said yesterday.

When she asked him about rumored connections in what Grenada officials hint was a CIA-connected coup, Riddick said he replied, "That's the biggest lie I've ever heard."

State Department sources scoffed at Grenada's claims that there was even any attempt at a coup at all.

"The U.S. had absolutely nothing to do with whatever occurred on the sleepy 133-square-mile island, according to one department source.

Riddick and her sister accompanied Cyrus' daughter, Susan Phillip, 18 when the Howard University freshman delivered to the Grenada Embassy a petition signed by 1,000 Howard students demanding the professor's release.

All three are citizens of the isolated patch of hills and jungle off the coast of Venezuela where about 100,000 people eke out a meager living from tourism and exports of bananas, nutmeg and cocoa.

For years, Grenada blushed at the erratic rule of Sir Eric Gairy, who became prime minister upon independence from Britian in 1974. Gairy, who ruled that island when it was a British colony, was noted for his impassioned speeches at the U.N. proclaiming the existence of UFOs.

In a coup that sent shock waves through the Caribbean, Gairy was overthrown March 13 by Bishop, 34, a British-trained attorney, and other members of the opposition New Jewel Movement.

Radix said Cyrus, 38, had gone to school with Grenada's current leaders.

The governemt, which U.S. officials say appears obsessed with rumors of attempted coups, said massive quantities of arms, explosives, Molotov cocktails and electronic detonators were recovered in breaking up the latest plot.

Cyrus was jailed last month during the first of two waves of arrests. The government also shut down the island's newspaper, The Torchlight, last week because, said a Grenada official, "it continued to publish lies and information that jeapordized national security."

Cyrus, a renowned scholar and imposing professor who is 6 feet 5 inches tall, weighs 270 pounds and goes by the nickname, "Santana," after his favorite Latin-rock band, has lost 35 pounds in prison, according to his sister. 'He's been drinking only tomato juice and tea," she said, out of fear of being poisoned.

She said her brother has had scant involvement in politics, his only foray into the political arena being a speech he made on behalf of Bishop's New Jewel Movement when it was an opposition party.