The cause of the collapses remains unknown. Possibly the choirs were pushed too hard for too long with not enough food and drink to sustain them, though no official explanation has been given as yet.
17 children were hospitalized and 9 remained in hospital by Sunday lunchtime, according to LSM, with 32 children in all needing medical attention during the final rehearsal.
As news of the collapses emerged, Education Minister Marite Seile said via twitter that a planned parade of participants on Sunday morning had been cancelled because "children's safety comes first".
1. #DzSv gajiens ir atcelts. Iemesli, kāpęc lielam skaitam bērnu šodien bija veselības problēmas vēl nav skaidri. Bērnu drošība ir galvenais
— Marite Seile (@mariteseile) July 11, 2015
However, it did take place as planned Sunday morning - though on a "voluntary" basis.
Prime Minister Laimdota Straujuma and newly-installed President Raimonds Vejonis (who participated in the 'unofficial' parade) said they would visit children still hospitalised.
But organizers of the event said the closing concert would proceed as planned.
In an official statement they said:
"Tonight's intended closing concert will take place as planned at 1900... the program length is 2.5 hours... In the concert will take part 13 000 singers, 800 dancers, 900 school brass band members, 800 folk singers, and 36 representatives of the diapsora.
"We invite parents and team leaders to carefully assess children's well-being, to keep up with weather forecasts and ensure appropriate clothing. The event will be attended by medics and emergency services."
Organizers told LSM's Latvian service on Sunday that in total 500 participants had received medical attention on Saturday, though most of these were for minor injuries.
Riga City council also expressed frustration with the lack of clear communication from organizers and government with mayor Nils Usakovs complaining that confusion about whether the event was on or off - and whether it was official or unofficial - made it difficult for council workers and officials to act accordingly.