Children stood around trucks in freezing weather, "so polite and civilized, asking if we had a biscuit," a United Nations aid worker said.
"The children we met are fed once a day with hot water and spices. Malnutrition is everywhere," the aid worker said.
The school is closed because children have too little energy to go, and the hospital is in someone's house.
"There is one general practitioner, a vet and two dentists, with a nurse learning on the job. Many of the hungry need the attention of doctors and must be treated slowly. Some want to cook the rice (the aid workers brought), but the children will be ill if they are fed suddenly," the aid worker said.
And even so, the people of Madaya offered to share their "siege soup," made of hot water and spices, with the aid workers.
"They insisted we eat it out of a sense of hospitality, but we refused as it is all they have," the aid worker said.
How did things get so bad in Madaya?
Madaya is surrounded by government forces and their allies. The last time it received aid was October 18.
Its fate is linked to a similar siege of the towns of Foua and Kefraya, which are surrounded by rebels.
But Madaya's plight has worsened since attacks on the nearby town of Zabadani have led to 10,000 more people flooding into Madaya.
Aid agencies have tried to help, but only after a sustained social media campaign did the U.N. manage to broker an agreement with the Syrian government to access the city.
Aid agencies have complained that their requests to access many areas in the devastated country are not honored by the warring sides.
Why does the aid have to go in by truck convoy? Why not air drop?
Air drops can only provide a limited amount. The distances by road are short and easy to cover, once access is permitted.
Air drops could be targeted by either side and might not reach those most badly in need. It's easier to send 44 trucks and they provide more help.
What is the situation in Madaya now?
The small amount of aid that got in may make a difference to those most badly in need. But those with serious malnutrition must be fed slowly or they risk falling ill.
There are 400 people in Madaya who urgently need to be evacuated for medical treatment, according to the U.N. These are the most chronically malnourished.
What happens next?
Aid agencies hope to get more food aid in on Thursday. The evacuation of those most badly in need was not part of the original deal, but is being urgently negotiated now.
Are there other Syrian cities in this situation?
Yes. Across Syria other towns are suffering similarly, besieged by regime or rebels.
The U.N.'s emergency relief coordinator, Stephen O'Brien, told the Security Council that 400,000 people across Syria urgently need food.