Around 900,000 tickets for the London Olympics, including men's 100m final tickets, have gone on sale, with priority given to those who missed out in two previous allocations.
Some 20,000 people had exclusive access to buy up to four tickets for a single event in a 31-hour period from Friday.
A million other unsuccessful applicants can purchase tickets from 13-17 May.
Some 70,000 general tickets for the Olympic Park will also be made available to this group from 17 May.
And from 23 May, unsold Olympic tickets of all varieties will be released for sale to the general public.
Locog said feedback from those users buying ticket from its website had so far been positive.
Seb Coe, chairman of Games organisers Locog, said: "We know thousands of sports fans were disappointed when they missed out in the initial sales period because of the massive demand for tickets.
"We promised we would prioritise these fans when we released the contingency tickets, which is exactly what we are doing."
Locog said they would give an update on the ticket situation when the current session finished on 17 May.
The online ticketing system came in for criticism after it crashed under high demand, leaving potential buyers frustrated at long delays.
In some cases, the system may have led buyers to believe they had been successful in their application, only to find out by email in June 2011 that they had failed.
The first priority group of 20,000 people are those who applied in the ballot and then the second chance sale but missed out in the latter, despite applying for apparently available tickets.
People in this group were contacted by Locog via email on Tuesday 8 May.
The 20,000 people contacted were able to select from any event, including the opening and closing ceremonies, although organisers warned that only a limited number of tickets were available for the two ceremonies.
Olympic Park tickets were not be part of the sale window for this group.
Fans from the two priority groups are limited to one transaction and a maximum of four tickets per person.
These restrictions will be lifted when the remaining tickets go on sale to the public.
New tickets for sale
From Sunday 13 May, one million people who missed out in the first ballot will have five days to buy tickets. Different tickets will be available from 11:00 each day, as follows:
- 13 May - Hockey, Tennis, Wrestling (Freestyle), Wrestling (Greco-Roman), Beach Volleyball and Football
- 14 May - Athletics (Race Walk), Athletics (Marathon), Canoe Slalom, Canoe Sprint, Shooting, Swimming, Volleyball, Weightlifting and Cycling (Track)
- 15 May - Equestrian (Dressage), Equestrian (Eventing), Equestrian (Jumping), Diving, Synchronised Swimming, Handball, Table Tennis, Swimming (Marathon) and Water Polo
- 16 May - Basketball (North Greenwich Arena sessions), Badminton, Sailing, Gymnastics (Artistic), Gymnastics (Rhythmic), Gymnastics (Trampoline), Judo, Taekwondo, Boxing and Fencing
- 17 May - Archery, Basketball (Basketball Arena sessions), Cycling (BMX), Cycling (Mountain Bike), Cycling (Road), Modern Pentathlon, Rowing, Triathlon and Olympic Park tickets
Tickets that are not sold each day will be carried forward for sale the next day. Once fans are successful they will be unable to buy any more tickets in the exclusive five-day period.
Unsold tickets for the Paralympic Games are also set to go on sale from 11:00 BST on 21 May, with further details yet to be announced.
And Locog has said it is releasing new tickets for sale from 29 May, to "help more people get to the Games". These tickets are:
- Cycling Road Race at Box Hill, Surrey
- Cycling Individual Time Trial at Hampton Court Palace
- There will also be tickets available for Wimbledon which will provide access to The Hill and the big screen only
- The Orbit - for those who already have access to the Olympic Park on the day they wish to visit the Orbit
Organisers have confirmed there will be a "babes in arms policy" during the Games, which means babies aged 12 months or under will be allowed into all London 2012 venues without a ticket - as long as they are securely strapped to a parent or carer.
But the policy will not apply to events held at Wembley Stadium, St James' Park, Old Trafford and North Greenwich Arena, where licensing rules require everyone to have a ticket.