MANILA, SEPT. 6 -- At least 19 government soldiers have died and 140 have fallen ill in what military officials said may have been a mass poisoning by communist rebels, Moslem separatists, or one of several insurgent terrorist groups on the strife-torn southern island of Mindanao.

Meanwhile, military officials today cleared the way to free most of the enlisted men involved in an abortive military coup nine days ago, despite earlier pledges that all involved would be punished.

The apparent mass poisoning occurred in Zamboanga City, more than 700 miles south of Manila. Officials said 225 new recruits for the Philippine Constabulary participated yesterday in a traditional "fun run" for about four miles and along the way, were offered ice water in plastic bags by an unidentified person.

At least seven of the military trainees died almost immediately, and officials at first suspected heat stroke.

Today, the death toll rose to at least 19. Military doctors said tests revealed that the recruits may have been poisoned during their jog.

"It is my opinion, based on my observation of the patients, that a lethal or toxic substance -- possibly pesticides -- might have been mixed with water and given to the victims," said Lt. Col. Dante Quibang, deputy commander of the military hospital in Zamboanga where the recruits were taken.

Brig. Gen. Lorenzo Rapanan, the regional commander, said there was "strong evidence of sabotage . . . by enemies of the state, leftists or extremists."

Mindanao, racked by a persistent communist insurgency, is also home to a number of Moslem insurgent groups who have been waging a protracted war for self-rule since the 1970s. Zamboanga City is a Moslem stronghold.

If confirmed by autopsies, the apparent poisoning would mark another in a recent series of setbacks for the Philippine armed forces, which are already in disarray following the failed coup attempt Aug. 28 and the death of a top general in an apparently accidental helicopter crash in Quezon province along the eastern coast of central Luzon island, where there are many communists.

The disunity in the military appeared to be worsening today with reports that a new group, Movement for Professionalism in the Armed Forces, has called for the dismissal of Gen. Fidel Ramos as the armed forces chief of staff.

The soldiers who staged the bloody revolt nine days ago were also asking for Ramos' ouster as their primary demand. The normally reliable Manila Chronicle reported in its Sunday editions that the new reform group was not linked to the Reform the Armed Forces Movement, which headed the abortive coup.

At the height of that 20-hour revolt, President Corazon Aquino said all those involved would be punished. Since the mutiny, 774 enlisted men and 35 officers have been detained, mostly on two Navy ships anchored in Manila Bay.

The government has faced at least four other coup attempts, and numerous other mutinies and rebellions, beginning with an abortive putsch at the Manila hotel in July 1986, but no soldier has been seriously disciplined.

Political analysts have said the lenient treatment of military coup plotters may have encouraged other disgruntled soldiers to try to overthrow the government. Most analysts agreed that the Aquino government risked losing its credibility if, once again, after the most serious and violent coup attempt, the perpetrators were released or given only mild punishment.

But military analysts said the government faced a dilemma in trying to punish the plotters. Hundreds of soldiers were involved in the simultaneous attacks on government installations in Manila, and hundreds more throughout the provinces expressed sympathy for the revolt. Harsh punishment for all the soldiers would have been time-consuming and cumbersome, and could have provoked a serious backlash within the divided military.

Today, a military spokesman said Ramos had approved a plan, prepared by his deputy chief of staff, Maj. Gen. Eduardo Ermita, that would allow a majority of the soldiers involved in the coup to be returned to their units.

In his report to Ramos, Ermita reportedly concluded that 65 percent of those detained were privates and privates first-class "who may be the least involved among the participants in the mutiny."

He proposed that those enlisted men be transferred back to their original posts for "retraining and reorientation so that they can be restored to normal duties."